martin



Dec. 4, 1928.

l T. G. MARTIN TELEPHONE SYSTEM 2 Sheets-Sheet 1 Us ww@ TEM@ Q .s m. Q .w Nufml -WuNmNruN m4 NDH Q* ma Dec. 4, 1928. v 1,693,613

T. G. MARTIN TELEPHONE SYSTEM Filed Feb. 1'7. 1926 2 Sheets-Sheet 2 Patented Dec. 4, 1928.

y UNITED srAres eraser 1F Fl C E TAIceo'r G. MARTIN, OF'CIIICAGO, ILLINOIS, AssIGNon, BY MnsNnAssIGNMENIs, 'ro

AUTOMATIO ELEC Taio INc., or CHICAGO, ILLINOIS, A CORPORATION on' DELA- '.iELnInoNE SYSTEM,

Appiication iedprebrua'iy 17, '1926. serial No. 83,793.'l

The present invention relates i to ,telephoneV systems in general, but vis concerned more particularly vvithsuch systems as have special means for informing the operator` ofthe class to which the calling Vsubscriber belongs.

lThis casemay beA considered Ian improveprivatenor'mal conductor'is. veryl likely' to Vbe induced 'on' anothery private normal conductor, owing tothe fact that, since it is a single conductor, Vthe private normal conductor can not be transposed likel a tivo conductor'vcircuit. It has beenfound also that,` to a' limited extent, the various tones von they private normal conductors find their vvay to the talking circuits, thereby e giving rise to undersirable'noises during con` versation." Accordingly, it is an objectof the invention to provide a nevvandimproved system in Which the tone currents are more nearly confined to their intended paths.

i a greater transfer of energy.Vv

v derstood.

in systemsi employing intermediate distributing frames betweenV calling lines and lineswitches, on` Yaccount of the fact that in such systems'the length of the lo'cal testl conduc torsV of the lines is much greater,`leading vto A further study ofthe situation appears to reveal that the transfer of energy from a private normal conductor of a busy line is scarcef lynoticeable on account of the .fact'that the private Vnormal conductor of abusy line is grounded, preventing a' high ltone voltage thereon. Therefore, if tone iskeptgofl'. the conductorsof idle'linesthe transfer'of tone current is prevented for all practical purposes Y Y e The particular arrangement employed to accomplish Athe foregoingobject consists in the provision of apair of contacts individua-l toeach line,`ivhich are arrangedto be closed only When the line is calling. This arrange. ment is shoivn in the accompanying drawings asA ap'pliedtoa plunger type linesivitch andthe tone applying contacts are controlledrby the plunger of the lineswitch so that the tone is disconnected from the local test conductor of the line except when vthe-plunger is in Vthe bank, thereby maintaining thetone-discon-V neet-edv except Whenthe line isa calling line. 'A' further object of the invention which naturally follows from the carrying out of the preceding one, is to limit the time during which the distinctive tone currentis flowing, thereby permitting muclrsmaller and -more easily maintained sources Vof tone current to be used. i

There" are various other-objectsof the in-4 vention which are concerned mostly with the circuit -details 'employed and Which will ybe fully appreciated upon a further perusal of the specification.

Referring novv to the accompanying'dravvings comprising Figs. l and 2, Sand 4,,there is shownk by means of the usual circuit diagramsa sufficient amount of apparatus in 'a telephone system embodying the` principles of the invention to enable the same to beim;

Fig. l shoivsthe lineswitch LS individual A g f yto the line of substation A, and the selector E. It has vbeen found in practice that'the Way `Fig. 2 shows the trunk circuit TC which is accessible to the selector E on one level and the Aassociated, trunk line comprising conductoi's llOyand lll. which extends v'to a distant ofice and there terminatesin the operators circuity OC. It may be assumed that the operator at the switchboard shown inthe drawings -is the regular toll recording opera'- tor which responds and records the necessary informationl when the subscriber desires a toll connection. kThis operator must fof' course ascertain if the calling subscriber is to be given toll service and'certain things` about the' class in` Which the' calling vline is placed.-y This information is gathered by the operator from listening tothe distinctive tone Vapplied 'fronithe test conductorof the calling Yline in'a manner to be h iiications of the is assumed that the primary windings of these transformers are connected, respectively, to

diierent distinctive tone sources. rlwo toner transformers are shown in the present-case,V

and as many others may be provided in any particular instance as required.

The invention having been described generally, a detailed description ot the operation ot the apparatus shown will now be given. For this purpose it' vill be assumed that the subscriber otsubstation A, desiring a toll connection, removes-his receiver and dials the digit assigned. to the toll lrecording' operator.r FJ hen the receiv r is renioyed at substation A, linev relay 12 ot the line switch LS encrgizes over the line conductors 2 and 3v of the calling line and 'through the resting contacts and armatures 10 and 11 of the coinbined pull-down andbridge cut-ott magnet- 8. Relay 12 energizes and at armature 13 closes a circuit tor'the pull-down winding of the magnet -8 including the open main conductor GM' controlled by the associated inaster switch'liiS. Upon the energization of the pull-down winding, the associated plunger arm .16 is attracted and it forces the plunger into the banks. Also, the armatures 10-and11 are attracted and they disconnect groundand line relay 12 from thea conductors ot the calling line. Relay 12, however, beine` slow acting, maintains its armature 13 attracted for an interval.

The line conductors 2 and 3 oi"- the calling line are now. extended to the corresponding conductors 2,7 and 29 leading to the associated selector E, and the private normal conductor isk connected to the corresponding conductorZS, thel release trunk conductor ot' the selector E. Accordingly line relay 35 or" the selector E energizes over the calling line and closes at armature 51 a circuit for release relay 36. Release relay energizcs and prepares vthe selector tor operation at armature 53 andat armature places ground on the release trunk conc uctor 28, thereby grounding the private normal conductor 5 ot the calling line, which makes the calling line busy in the banks ot the connectors having access to it through the terminals Z and other multiple terminals. As another result et the grounding oit release tiiunk conouctor 28, a circuit is closed through the bridge cut-oit winding of magnet 8 so as to maintain the armature 15 operated and to maintain the bridge cut-ott armatures and 11 attracted after the slow acting relay 10 falls back. It will be noted that tone current from the secondary winding of the transformer may now flow over the private normal conductor 5 ot the calling line and over the release trunk conductor 28 of the trunk line leading to the selector E. There is no danger ot elec.,- trostatic induction taking place to transfer the tone' to adjacent conductors, however, owing to the tact that release trunk conductor 28 is at present grounded at armature 52 in the selector E.

When the calling subscriber operates his device 4in accordance with the digit necessary to trunk the cal to the toll recordingoperator, the circuit ot line relay '35 is opened" a corresponding number ot times..

Eachtiine. line` relay deenergizes in response to one'ot the interruptions thereby produced, it closes a circuit 'tor vertical magnet 40 ras Yfollows `from ground Yby way of the resting contact otarinature 59and said armature, armature.51` and its resting con act, armature 53 and. its working contact, relay 37, and vertical magnet l0 to'battery. By the operation of vertical magnet 40, the wipers 61,-63, inclusive, are raised opposite the de'- siredylevel of bank contacts. Relay 3'? is enerfrized in series with vertical magnet i0 and, being slow-acting, retains. its armature attracted throughout the vertical movement. As a resultotkthe energization et relay 37, a circuitis closed at armature liet-for stepping relay 38 by way. of, oiit normal'contacts 43 (which close upon the lirst vertl`cal step) and interrupter contacts 42, Stepping relay 38, upon energizing, closes alock-ing circuit for itself at armature 55, and-at armature 5G prepares ay circuit .for rotary .magnet l1.

Attheend ofthe vertical movement, slowacting relay 37 deenergizesv` and completes the circuit otrotary. magnet lat armature 54. Rotary magnet 41, upon energizing, advances the wipers 61'63, inclusive, into engagementwith therst set. oit-bank contacts in the selectedlevel,` and, near the end of its stroke, opensthe circuit lofV stepping relayY 38 at interrupter. contacts 42. Stepping relay 38, upon deenergizing, opens the circuit ot rotary magnetlil at armature 56, whereupon rotary magnet 41 deenergizes also and closes its interrupter contacts again. ln case. the trunk terminating in the first set-of bank contacts is idle, switching relay 39 energizes immediately. Assumingthe trunk to be busy, however, switching relay 39 is short-circuited by the ground potential encountered byY test wiper 6.2, and steppingvrelay 38 energizes from this same ground potential and closes the circuit of rotary magnet d1 again, whereupon the switch wipers are rotated into engagement with thenext set of bank contacts. This alternatev operation of stepping relay 38v and rotary-inagnet41 Continues until an idle trunk is reached, which trunk it will be assumed is the one. terminating Ain bank contactsl (ie-66;, inclusive, whereupon switching relay 39,being no longer short-circuited, energizes in series, with stepping relay 38. Stepping relay 38, however, does not energize at this time on account or" the highresistance of switching relay 39. Switching relay 39, upon energizing, opens a point in the test circuit and; prepares the holding circuit at arma-ture 58; disconnects grounds from arma lli) ture 51 of line relay 35 at armature 59, thereby opening thefcircu'it of release relay 36; and

at armature 57 and 60 disconnects conductors 27 and 29 from the windings of line relay 35,

and extends themby way ot' wipers 61 and 63,

bank contacts 64y and 66 and trunk concluetors 67 and 69 to thev windings of line relay 101 of the trunk circuit TC. Line relay 101, upon energizing, closes a circuit for release relay Y 102 at armature 104, whereuponzrelease relay 102 energizes and places ground onv release trunk conductor 68 at armature 106, thereby .e'stablishingthe usual holding circuit for the switching relays of the line switch C and the selector E before the slow acting release relay 36 of the selector E has had time to deenergize.

As a further result of the energization 'of line relay 101, ground is placed on' the lower winding of the marginally ladjusted back bridge relay 103 at armature 105, thereby closing a circuit over the' inter-office trunk conductors 110 and 111 and through Vresistance 135 and r`elay134 to the toll recording operaftors position. VRelay 134 energiZesl over this circuit, but back bridge relay 103 does not energize on account of the high' resistance 135.

' Relay 134, upon energizing, closes at armature 136 a. circuit for the answering lampiL, which circuit includesspring131 of thekey K and its lower contact, and spring 133 and Vits lower contact. The lamp L accordingly becomes 'light-'ed to inform the operatorotl the call.

rlhe operator,^uponnoting the lighted condition of the lampl L, manipulates her listenling key K', thereby connecting her 'listening' taps to the trunk conductors 110 and 111. ln crderto hear the tone theV operator throws the key K in such a direction as to operate springs 131V and 132.

and spring 132 placesa shunt around t-he high .resistance 135, whereupon the marginally adjusted :back bridge relay 103 'of thetrunk circuit TC energizes Aand at armature 107 Vshift-s the release trunk conductor 68 from` ground at the normally closed contacts con? trolle'd by armature 107 toground through the primary windingv of the induction coil 109. At armature 108, relay 103 places a. bridge across the outgoing trunkconductors including the secondary winding'ofthetone transformer 109, and the associatedconductor in series. By this operation the'tone current owing in conductor 68 passesto the talking y conductors and is heard by the operator.

After thel operator has noted the` class of the calling line, she throws the key to the opposite position, therebyV restoring the springs 131 and 132 andoperating spring 133.

Spring 133 takes over the function of spring 131, and spring 132 reinserts the resistance 135 in the circuit, whereupon the marginal back bridge relay 103 in the trunk circuit "lC restores and disconnects the primary winding of the transformer 109 from the releasetrunk Spring 131 disconnects 4 the lamp L and prepares another circuit for it conductor 68, at the same time ,the

It may be noted' that yarmature 108 disconnects the secondary winding of the tone transformer from across the talking conductor so as to prevent unnecessary sliunting loriginal ground source to the' release trunk conductor.

or" the talking current at this point during ing operator isterminated, line relay 101 'of the trunk circuit TC deenergizes andv opens the'circuit of relay 134 ofthe operators cir# cuit OC. Relay 134th ereupon deenergizes and completes acircuit'for the lamp L which includes the upper contact of spring 133 of the key K and said spring, lower contact of spring f 131 *and said spring, andV armature 136'and its resting contact. l

The cperator,upon not-ing the lightedcon` dition of the lamp L, knows that 'the calling she accordingly restores the key K.

subscriber has nowreplaced his receiverand Y As a. Vfurther result of thedeenergization ofV i line relay 101 of the trunkcircuit TC, the

circuit `of release relay 102 is opened at armature 104. Release relay 102, upon deenergizing, removes ground.y from release l,

trunk conductor 68 at armature 106, whereupon magnet 8 of the line switch LS andthe "switching relay of lselector E, Fig. 1. deenergi'ze. The deenergization otinagnet 8 vot the line switch LS resultsin the restoration of the circuit conditions in the line switch to normal,4 and the `deenergization .of switching relay 39 ofthe selector E results in a circuit being Vclosed at armature 59 and through armature 51 and its resting contact, armature land its resting contact, and off normal acont-acts 45 for release magnet 44. Release magnetV 44v thereupon energizes and the wipers of the switch E are restored to normal Y position in the usual manner, whereupon'the circuit ot release magnet 44 isvopened at off normal contacts 45. v F rom the above itcwill be Seen howy the `operator is enabled to listen to the tone -placed o-n the line of substation A at the exy vrchange in accordancewith the class thereof. j`

It is ALperfectly. obvious if the line of substation app-ropriatetone connection may be made, or

tone may be eliminated entirely, depending `is laterchanged to another class, the

upon the class to which the line is changed.

When the line of lsubstation A is. called through the terminals 7 the placing of ground potential on the private normal Vcon-` ductor 5 results in the e'nergization of theV B. C. O. winding ofthe magnet 8 and inl the operation of thebridgebutfoil' arma.-

tures l0: and ll, but the plunger' arm is not operated as is Well known. Therefore, the tone source is not connected. up.

In casel it is desired to have the tone source connected up when the line is called, as Well.

C.. 0.A armature springs l0 and ll. Fig, 8 shows how the connect-ions are made.

Another modification is shown in Fig. 4. Referringto this latter figure, ifv it is desired to have the tone connected up only when the line is called, spring- 9 may be provided with a normally engaging contact spring and the Contact pair Yso ''orined are connected in Seriesavith the above mentioned normally open springs in the C. assembly.

lVhat is claimed is:

l. ln a telephone system, telephone lines of different character, a local `conductor for each line, tone sources of different character, and automatic line switches adapted when actuated by calling linesto connect their local conductors tothe corresponding tone sources, and when releasedto disconnect said local conductors.

2. ln' a telephone system, telephone lines of different character, a local conductor for each line, tone sources of diilerent character tor said lines, and plunger line switches having contacts actuatedby the movement of the plungers When actuated by calling lines to connect their local conductors to the corresponding tone sources, and released to disconnect said local conductors.

3..n a telephone system, telephone lines, a central oi'y'nce Wherein'said lines terminate, local conductors therefor at said central otce, calling and called terminals for said local conductors, an intermediate distributing frame `for facilita.ting interconnection of said terminals, a tone source at the central office., and means actuated on originating calls only for applyingtone currentl tov the local conductors.

4. ln a telephone system, telephoneflines, a central cnice wherein `said lines terminate, local conenctors therefor at said central office, calling and called terminals tor said local conductors, an intermediate distributing trame for facilitating interconnection oi' said terminals, a tone source at the central oiliee, trunk lines. automatic switches for extending calling lines to said trunks, and means controlled nesesito by said automatic switches for applying tone current to the local conductors.

5. ln a telephonesystem, telephone lines` line relays forsaid lines, a central ollce wherein said Alines terminate, local conductors Jfor said lines atsaid central oice,.calling and called terminals. tor said -localfconductors a tone source at the central ollice, trunk lines, line switches for said telephone lines, means 'for actuating said line switch upon the energisatio oi the line relays on originating calls to extend the lines to idle trunks and to connect the local conductors thereof to said tone source, and means actuated by the closure of called` lines for disconnecting their line relays without connecting said source to the called line local conductors.

6. in a telephone system, telephone lines or different character, means by which an operator can answer calls from any of said lines, means for indicating to the operator the character oli the calling line including an identifying circuit i r. connection With apparatus individual to said lines, and means for closing vaid circuit only on originating calls.

T. ln a telephone system,telephone lines or diii'erent character7 means whereby an operator may answercalls from any of said lines, means indicating to the operator the character oil' the calling line Aincluding -a tone source connection with the sleeves of the lines, and means for applying the current from said source to said sleeve on originating calls only and forv preventing said tone current from standing on the sleeves VWhen the lines are idle.

8, lnl a telephone. system, telephone lines oi different character, an individual line s itch including a local conductor for each line, a tone source for certain of said lines, and means actuated responsive to either an incoming or outgoing call over one of said lines for connecting its local conductor to said source.

TALBGT G. MARTlN. 

